1. Field of the Invention
The present invention relates to a projection display device such as a projector that includes a cooling device for cooling an illuminant of a light source. More specifically, the present invention relates to a projection display device that always is capable of cooling a high-temperature portion of a light source lamp even in various installation postures.
2. Description of Related Art
Conventionally, a projection display device such as a projector includes a light source lamp that emits light for projecting and displaying an image displayed on a display device such as a liquid crystal panel. This light source lamp is filled with mercury, an inert gas, a metal halide, and the like.
In this projection display device, when a predetermined voltage is applied to electrodes of the light source lamp, a discharge arc occurs, and the gas filled in the light source lamp starts to be convected.
The discharge arc being carried by the convection is formed into an arch shape in a chevron pattern to approach the top of the light source lamp, which makes the temperature at the top of the light source lamp higher.
When the light source lamp has an excessively high temperature, problems such as whitening, a shortened life, and a rupture occur. To the contrary, when the light source lamp has an excessively low temperature, problems such as blacking and lower brightness of the light source occur.
In view of the above, various methods have been proposed for cooling the top of the light source lamp efficiently. Usually, cooling air is blown toward the vicinity of the top of the light source lamp. More specifically, ambient air that is drawn in for cooling from the outside of the device by a cooling fan is guided by a guiding means (air guide path) such as a duct, thereby cooling the top of a light bulb that reaches a high temperature.
Even when the projector is installed in a somewhat different posture depending on its projection condition, the light source should be held with its electrodes kept horizontal. For this reason, the light source is disposed so that a lamp axis that connects the two electrodes of the light source lamp is orthogonal to an optical axis of a projection lens. Accordingly, the electrodes are prevented from being raised or lowered due to a difference in the posture of the projector, and a stable light-emitting position is obtained, resulting in conformity with optical properties. However, the light source lamp is inverted depending on whether the projection display device is used in a floor-standing state or a ceiling-hung state.
For this reason, even with the configuration for cooling the top of the light source lamp efficiently, the projection display device is caused to cool predominantly at the bottom of the light source lamp depending on its installation posture, i.e., if the projection display device is turned upside down, resulting in an excessively low temperature at the bottom of the light source lamp.
Similarly, when the projection display device is used in a posture for projecting an image in a vertically upward direction, a posture for projecting an image in a vertically downward direction, or a posture therebetween, portions other than the top of the light source lamp are overcooled, which causes blacking and lower brightness of the light source.
In this case, the top, which needs to be cooled, in contrast is cooled insufficiently, which contributes to enhanced cooling. As a result, the above-described phenomena are worsened.
In order to solve this problem, JP 2002-298639 A, JP 2005-24735 A, and JP 2007-78736 A disclose a method in which an angle of a baffle plate is changed depending on an installation posture of a device, thereby cooling the top of a light source lamp efficiently, and a method in which a plurality of cooling air ducts are provided, so that an appropriate flow path is selected depending on an installation posture.
A light source device disclosed in JP 2002-298639 A above includes, in the vicinity of a side surface of a front opening of a concave mirror, a wind direction control plate for supplying much ambient air to the top or bottom of a light source, thereby cooling the top of the light source even if a projection display device is turned upside down.
However, since air is supplied from a lateral side direction, even if the light source lamp has an optimum temperature at its top and bottom, the temperature on both lateral sides of the light source lamp becomes higher or lower than that at its top and bottom.
Further, a light source device disclosed in JP 2005-24735 A includes cooling air inlet openings on top and bottom surfaces of a concave mirror. Each of the cooling air inlet openings is connected with a cooling air path. At an entrance of the cooling air path, a shutter that makes up-and-down movements under its own weight is provided.
However, it is necessary to form the air duct for cooling a light source at both the top and bottom of the concave mirror, which makes the device larger.
According to JP 2002-298639 A and JP 2005-24735 A, the light source lamp has an optimum temperature at its top even if the projection display device is turned upside down. However, when the projection display device is directed vertically upward or vertically downward to project an image, it is impossible to cool the top of the light source lamp.
Further, in a projector device disclosed in JP 2007-78736 A, two air inlets for introducing cooling air toward a light source lamp are formed on both lateral sides of a plane including a central axis of the light source lamp and orthogonal to a side wall of a concave mirror.
However, since cooling air is blown from one direction, the temperature on both lateral sides of the light source lamp becomes higher or lower than that at its top and bottom. Additionally, in a certain installation posture, the light source lamp is cooled excessively at its bottom.